1. Field of the Invention
The invention relates to a geared motor having a motor unit and a change gear unit for transmitting rotational power from this motor unit in combination, and a geared motor series from which this geared motor can be constructed.
2. Description of the Related Art
Geared motors comprising a motor unit for generating rotational power and a change gear unit for reducing or increasing the speed of the rotational power in combination are widely used in every industrial field, because their motor speeds are mechanically reduced or increased, they are capable operating their motor units in a most efficient state (revolution range).
For example, a conventional geared motor 1 shown in FIG. 10 comprises a motor unit 2 and a change gear unit 4 for transmitting rotational power from the motor unit 2 in combination.
This motor unit 2 has a mounting surface consisting of a square motor flange 10 formed thereon at the top side of its motor shaft 6. This motor flange 10 has bolt holes 10A formed therethrough at the four corners. The motor shaft 6 is located at the center of the motor flange 10.
The motor unit 2 outputs rotational power through the motor shaft 6. As shown in FIG. 9, the end of this motor shaft 6 is splined so as to support a helical motor pinion 8 rotatively.
The change gear unit 4 has a three-stage reduction structure. Specifically, the change gear unit 4 comprises: a first gear 12 meshing with the motor pinion 8; a first pinion 14 for making coaxial, integral rotation with the first gear 12; a second gear 16 meshing with the first pinion 14; a second pinion 18 for making coaxial, integral rotation with the second gear 16; an output shaft gear 20 meshing with the second pinion 18; an output shaft 22 supported by a bearing, for making integral rotation with the output shaft 22; and a casing 24 for accommodating these change gear mechanisms.
A shaft insertion hole 24A to which the motor shaft 6 is inserted is formed through the casing 24. The casing 24 is also provided with tapped holes 24B formed at the individual corners of a square with the shaft insertion hole 24A at the center. The shaft insertion hole 24A and the four tapped holes 24B are arranged to coincide with the motor shaft 6 and the four bolt holes 10A in the motor flange 10 of the motor unit 2, respectively, so that the motor unit 2 and the change gear unit 4 are coupled to each other by four bolts 26, as shown in FIG. 10.
In this geared motor 1, rotational power from the motor unit 2 is transmitted through the individual pinions and gears to the output shaft 22 at a predetermined reduction ratio.
For this type of geared motor 1, in general, a plurality of serialized change gear units 4 set at change gear ratios with predetermined intervals (common ratios) are provided in advance. Of these, one change gear unit 4 having the change gear ratio closest to an actually-required change gear ratio is combined with the motor unit 2 to construct a geared motor 1.
As described above, a user of the geared motor 1 selects a change gear unit 4 having the most appropriate change gear ratio from among the series with a variety of change gear ratios. According to the use patterns of the geared motor 1, however, a modification to the change gear ratio is sometimes needed afterwards. Possible measures to be taken here include the following:
1) Replace the change gear unit 4 with a new one having an optimum change gear ratio
2) Add a change gear unit having an adjusting change gear ratio to between the change gear unit 4 and the motor unit 2.
The measures 1), however, require purchase of the new change gear unit 4, giving rise to an increase in cost and a problem of wasting the change gear unit 4 used heretofore.
As for the measures 2), the change gear unit 4 used previously was intended for to-motor coupling in the first place. Therefore, the interposition of a change gear unit between the change gear unit 4 and the motor unit 2 was often difficult in practice, and involved considerable problems. The reasons therefor will be described in concrete terms hereinafter.
A first problem is that the change gear unit 4 has a mounting surface structure of xe2x80x9creceivingxe2x80x9d type alone, and hence it is physically difficult to couple an additional (other-than-motor-unit) change gear unit or the like (hereinafter, referred to as insert unit) thereto.
A motor unit 2 is always coupled to an apparatus to be driven (mating machine) such as the change gear unit 4. To facilitate this coupling, there is typically provided a motor flange 10 as shown in FIG. 10. This aims to insert bolts 26 to the bolt holes 10A from the motor side, and threadedly engage the bolts 26 with the tapped holes 24B on the mating-machine side to allow the coupling.
As a result of this, many reduction gear units 4 simply have a structure of xe2x80x9creceivingxe2x80x9d it. More specifically, reduction gear units 4 often have nothing but simple tapped holes 24B formed at the individual corners of a square around their shaft insertion hole 24A to which the motor shaft 6 is inserted; that is, there is little assumption that the coupling may be established by bolting from the reduction-unit-4 side.
Turning now to an insert unit itself, suppose that the change gear mechanism in the insert unit has a parallel axis gear structure containing pinions and gears in combination. In a single-stage reduction mechanism, it would be impossible for the insert unit to establish coaxiality between the motor shaft 6 inserted thereto and its own output shaft for transmitting the rotation of the motor shaft 6 to the reduction gear unit 4. Therefore, two or more stages (two or more pairs of gears and pinions) are logically required in order to make coaxial the motor shaft 6 and the output shaft in the insert unit. The insertion unit thus becomes complicated in internal structure, as well as extended along the axial direction of the motor shaft 6.
A second problem is that even though the main objective is to make an adjustment in change gear ratio, it is not always possible to achieve a user-intended change gear ratio.
Change gear units, as described before, are serialized with change gear ratios of regular intervals in advance. Therefore, combining the same with serialized insert units of another types cannot always achieve a desired change gear ratio. That is, combinations of change gear ratios obtainable from ordinary geared speed-change units lead to only a limited variation of change gear ratios, failing to make fine adjustments according to an actual change gear ratio needed.
A third problem is that combining two change gear units increases noise greatly. To be more specific, there occur the problems that the change gear units combined produce resonance with each other, and that a rise in the number of gears makes the gears themselves produce higher noise.
The present invention has been achieved in view of the foregoing problems. It is thus an object of the present invention to provide a geared motor which can meet user needs for change gear ratios with flexibility and reliability as well as suppresses an increase in noise, and a geared motor series from which a plurality of types of such geared motors can be constructed.
The invention according to claim 1 achieves the foregoing object by the provision of a geared motor comprising a motor unit and a change gear unit for transmitting rotational power from the motor unit in combination, the change gear unit being arranged with its input shaft coaxial to a motor shaft of the motor unit, wherein: a simple planetary roller unit including a simple planetary roller mechanism and a casing for accommodating the simple planetary roller mechanism is interposed between the change gear unit and the motor unit, the simple planetary roller mechanism having a sun roller, a planetary roller retained by a carrier, and a ring roller, the planetary roller making rolling contact with the outer periphery of the sun roller and with the inner periphery of the ring roller; and flange portions spreading outward in the radial directions of the sun roller are formed on the casing for accommodating the simple planetary roller mechanism, at both ends in the axial direction of the sun roller, and one of the flange portions is coupled to a casing of the motor unit and the other is coupled to a casing of the change gear unit, and the geared motor is configured so that rotational power from the motor unit is coaxially transmitted to the change gear unit through the simple planetary roller unit.
This geared motor adopts a simple planetary roller mechanism as the insert unit. The simple planetary roller mechanism is capable of fine adjustments to the outside diameter of its ring roller, and therefore can flexibly meet a more delicate change gear ratio as compared with geared speed change structures which are controlled by the numbers of teeth, modules, and the like. Besides, this simple planetary roller mechanism has the advantages that its input and output shafts can be easily made coaxial, and that higher change gear ratios can be obtained from a compact configuration.
Then, the present inventors has found that the characteristic configurations of the simple planetary roller mechanism and the casing supporting the same can be utilized to provide a flange structure on both sides, and has conceived that it is thereby possible to solve a number of problems existing heretofore, such as noises and fine adjustments to the change gear ratio, in whole.
More specifically, in this geared motor, the casing for accommodating the simple planetary roller mechanism has a double-flange structure. Therefore, even if the mating machines (change gear unit, motor unit) have structural difficulty in being coupled to other units, the flanges allow easy coupling therebetween. The reason is that it is possible to insert coupling bolts from the flange sides and threadedly engage the same with tapped holes in the mating machines.
By the way, it is publicly known, in the sense of general concepts, that transmission apparatuses comprising traction rollers can reduce noise as compared with geared transmission apparatuses. When the present inventors adopted a transmission apparatus of simple planetary roller mechanism and interposed this simple planetary roller unit to between a reduction gear unit and a motor unit, however, they found an unexpected noise reduction effect that the total noise becomes significantly lower than before the interposition, i.e., when the change gear unit and the motor unit were directly coupled to each other (U.S. patent application Ser. No. 09/526,284).
Although there are many uncertainties, the reason for this seems to be that this simple planetary roller mechanism has a characteristic power transmission structure utilizing the rotations and revolutions of its planetary rollers, and transmits rotational power by means of friction between the contact surfaces of (the plurality of) rollers. Here, the individual contact surfaces and the portions supporting the planetary rollers can well absorb the vibrations and noises which used to occur from the resonance between the motor unit and the change gear unit. In any case, the effect of noise reduction is as dramatic as far beyond expectations.
Moreover, as a result of forming flange portions on both sides of the casing, it becomes possible to couple any motor unit and change gear unit across the flange sides, permitting easy provision of a geared motor series including a variety of combinations. That is, since the two flange portions may be formed into different configurations (different bolt arrangements), even such motor units and change gears unit as never used to be combinable can be coupled to each other through the interposition of this simple planetary roller unit. This allows the provision of a wide-ranged geared motor series.
Besides, upon the interposition of this simple planetary roller mechanism to between a motor unit and a change gear unit coupled previously, both of the flange portions may be provided with a plurality of bolt holes formed therethrough along the axial direction of the sun roller so as to be identical to each other in arrangement. Then, mounting bolts inserted to the bolt holes may couple one the flange portions to the casing of the motor unit and the other to the casing of the change gear unit.
Of course it is also possible that both of the flange portions are provided with the above-mentioned bolt holes in different arrangements as well as those bolt holes in identical arrangements. This provides further versatility for applications.
Moreover, in the foregoing invention, the ring roller may be fixed to the casing for accommodating the simple planetary roller mechanism so that the rotation of the ring roller is restrained. Then, a shaft insertion hole is formed on (or through) the rotational center of the sun roller, and either the motor shaft of the motor unit or the input shaft of the change gear unit is inserted to the shaft insertion hole. A shaft insertion hole is formed on (or through) the rotational center of the carrier, and the other of the motor shaft and the input shaft is inserted to the shaft insertion hole. Thereby, rotational power from the motor unit is coaxially transmitted to the change gear unit through the simple planetary roller mechanism.
According to this invention, it is possible to install the simple planetary roller unit in place of a coupling which used to couple the motor shaft and the input shaft of the change gear unit. Therefore, the simple planetary roller unit offers the same functions as those of a shaft coupling even after the addition of speed change function.
Incidentally, xe2x80x9cchange gear unitxe2x80x9d employed in the present invention means a unit that changes the rotational speed of input rotational power for output, including a reduction unit, a step-up unit, and the like.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.